The present invention relates to the strengthening of silicate glass laser rods by a method of treating which provides a surface that is stable against thermal shock and that does not interfere with light pumping through the sides of the treated rods.
In the manufacturing of glass laser rods, certain imperfections result which must be removed or corrected by special procedures; otherwise, the laser rods yield less than the desired results. For example, the glass laser rods are generally cut with a diamond tool. The cutting and finishing procedure generally leaves incipient fractures from a number of causes; i.e., diamond tool cutting marks, imbedded surface inclusions, shatter marks, spontaneous fractures or incipient cracks resulting from uneven strain distribution. The surfaces are generally ground and polished with a fine abrasive material to remove the larger cutting marks and imperfections. The diamond tool cutting marks are generally ground away with a 180 grit abrasive material (e.g. corundum, emery, or the like). The quality control procedure used to evaluate a finished glass laser rod includes heating the rod to a temperature of about 250.degree. to 300.degree.F in an oil such as a silicone oil (e.g., DC 200) and then plunging in water at about 80.degree.F. If a laser rod withstands this gradient test, then it is generally considered acceptable for extended use. However, a high percentage of the failures of prior art rods were due to cracking, and if the strain distribution which caused cracking were quite uneven, the rods would fall completely apart under conditions of thermal shock exposure.
Glass laser rods in the past have been subject often to damage by physical abrasion and thermal shock since they had not been prior conditioned to withstand these forces. The usefulness of laser rods depends on their ability to withstand thermal shock and on how well light can be transmitted at particular wave lengths. Flaws can effect the efficiency and usefulness of laser rods. Flaws which have been commonly referred to as Griffith's flaws have rendered the glass laser rods inefficient. Attempts to seal these flaws and still not interfere with light pumping through the sides of the treated laser rods has been a problem which the laser art has been challenged to solve.
Therefore, an object of this invention is to provide a method of increasing the strength of glass laser rods to withstand thermal shock.
Another object of this invention is to provide a method of treating and strengthening glass laser rods which seals flaws and enables light pumping to be accomplished through the sides of the treated and strengthened glass laser rods.